There are many types of limited use or disposable protective fabrics designed to provide barrier properties. One type of protective barrier fabric is a laminate of a film and a nonwoven material. Such materials can be used to effectively seal off a wearer from a harmful environment in ways that conventional textiles and/or nonwoven materials are unable to do.
Disposable protective fabrics should be resistant to liquids and solvents. For a variety of reasons, it is undesirable for hazardous substances and/or pathogens which may be in liquid form or carried by liquids or aerosols to pass through a protective fabric to contact persons working in an environment where such hazards are present.
After use, it is usually quite costly to decontaminate protective clothing that has been exposed to a harmful or hazardous substance. Thus, it is important that a protective garment be inexpensive so as to be disposable.
Generally speaking, inexpensive laminates can be made from films and fibrous nonwoven materials. In some cases, these laminates may be adapted to provide useful barrier properties. Although the nonwoven fibrous web component of the laminate may provide some barrier properties, it is usually the film component which serves to block penetration of the laminate by hazardous substances.
One problem associated with laminate construction is poor inter-ply attachment (i.e., bonding between the plies which holds the laminate together). Thermal bonding is one way to attach plies but is problematic if the plies are formed of incompatible materials. Combinations of thermoset materials and thermoplastic materials are usually unsuited for thermal bonding. Thermal bonding may also be difficult to accomplish when certain combinations of polymer materials are used. For example, low density polyethylene films have proven relatively difficult to bond to polypropylene fibrous nonwoven webs. Thermal bonding presents other problems when relatively thin films are used. It can be difficult to bond thin films without damage which may impair their barrier properties. This has economic implications since the film is often the most expensive component of the laminate. Reducing the film thickness would help reduce cost.
As another example, some types of microporous and/or microapertured films often have latent internal stresses resulting from the microporous and/or microapertured film manufacturing processes. These internal stresses can render such films susceptible to shrinkage when exposed to temperatures capable of softening the films. Such exposure may occur during many types of conventional bonding processes to join these specialized films to other materials. Shrinkage of these films is highly undesirable because it can affect the barrier and/or breathability of the films, cause gathering or puckering of the film, and/or increase the amount of film required to produce a given area of laminate material.
Adhesives may be used to join the layers of the laminate. Solvent-based adhesives can present environmental and safety problems because they contain volatile organic compounds. During laminating and drying, large amounts of solvent vapor may create exposure hazards and could be subject to environmental regulations. On the other hand, water-based adhesives may fail to provide adequate inter-ply attachment. Water-based adhesives may also have inadequate resistance to solvents. Whether solvent-based or water-based, the adhesives must be suited for the high-speed manufacture of protective barrier fabrics at such low cost that may be economical to discard the fabric after only a single use. In conventional processes that use water-based adhesives to bond materials, the materials and adhesive are exposed to heat in order to cause or speed up drying, curing or setting of the adhesive. The levels of heat required are typically unsuitable for temperature sensitive films.
Thus, a need exists for a practical process for making an inexpensive limited use or disposable water-based adhesive bonded, solvent resistant protective film/nonwoven protective laminate having desirable barrier properties and which is tough, durable, and lightweight. This need also extends to a practical method of making such a laminate which utilizes a water-based adhesive. This need further extends to a practical method of making such a laminate which utilizes a water-based adhesive and which is suitable for temperature-sensitive materials. Meeting this need is important since it is both economically and environmentally desirable to substitute water-based adhesives for solvent-based adhesives thereby avoiding the need for expensive solvent recovery equipment to control emissions of volatile organic compound into the work-place or outside environment. There is also a need for an inexpensive, limited use or disposable water-based adhesive bonded, solvent resistant protective film/nonwoven laminate designed to provide barrier properties. There is also a need for an inexpensive limited use or disposable water-based adhesive bonded, solvent resistant protective film/nonwoven laminate having desirable barrier properties and which is tough, durable, and lightweight. For example, a need exists for an inexpensive, limited use or disposable water-based adhesive bonded protective film/nonwoven laminate that resists liquids, is durable and conformable, has useful levels of inter-ply attachment even after exposure to solvents and/or solvent vapors and which has practical applications in protective apparel.